The present invention relates to apparatus for indicating the level of liquids in and for preventing the overfilling of containers. More particularly, the invention relates to improvements in apparatus wherein the level of liquid in a container is monitored by a float or an analogous buoyant level detecting device. The apparatus of the present invention can be utilized with advantage for indicating the level of liquid in and for preventing the overfilling of compartments in watercraft, for example, to prevent overfilling of tanker compartments with volatile liquids whose vapors are readily combustible.
It is known to monitor the level of liquid in a container by means of a float or an analogous buoyant element which swims on the surface of the body of liquid and rises or falls, depending upon whether the container receives or discharges liquid. It is also known to couple the float with a piston which influences the pressure of a gaseous fluid (e.g., air) in a closed pneumatic system. The pressure of confined gas rises in response to rising level of liquid in the container. When the pressure of confined gas reaches a predetermined maximum permissible value, an actuating device which is directly or indirectly subjected to the pressure of confined gas closes a shutoff valve in the pipe which admits liquid into the vessel. A drawback of such apparatus is that each and every valve of a battery of shutoff valves must be coupled with a discrete actuating device. This contributes to the initial and maintenance cost, for example, when the liquid is to be admitted (via separate pipes) into each and every compartment of a large watercraft.